Venomous Fish Species Found To Be Widespread, Outstripping Count For All Other Venomous Vertebrate Species, Including Snakes

Venomous Pterois Lionfish

Most people conjure snakes, scorpions, or spiders when they think of dangerous, venomous creatures. New work by two American Museum of Natural History biologists, however, shows there are more species of venomous fish than venomous snakes; in fact, there are more venomous fishes than all other venomous vertebrates combined.

The new study replaces the old estimate of 200 species with a conservative estimate of more than 1,200 species of venomous fish, including lionfishes, catfishes, scorpionfishes, weeverfishes, toadfishes, surgeonfishes, scats, jacks, rabbitfishes, stargazers, and stonefishes. The new finding is described in the Journal of Heredity by William Leo Smith, Postdoctoral Fellow in the Museum's Division of Vertebrate Zoology, and Ward C. Wheeler, Curator in the Museum's Division of Invertebrate Zoology.

"The results of this research were quite surprising," said Dr. Smith. "They indicate that more than 1,200 fish species should be presumed venomous, and we were able to corroborate this estimate by a detailed anatomical study examining potentially venomous structures in more than 100 species. Our results now suggest that more than 2,000 species of vertebrates are venomous. This tripling in number of venomous vertebrates comes exclusively from ray-finned fishes, making 'bony fishes,' not snakes, the most diverse group of venomous vertebrates."

Venomous Paracanthurus Surgeonfish

Venomous fishes pose a serious threat to humans with more than 50,000 reported injuries due to envenomations per year, with symptoms ranging from blisters to intense pain, fever, or death. This new worka large-scale molecular and morphological analysis of spiny-rayed fishes (fish with true fin spines), based on 233 species and more than one million nucleotides of DNAis the first to examine the evolution of venomous fishes.

The results have implications for human health, as venoms from various animals including fish have a wide range of pharmacological effects on human nervous, muscular, and cardiovascular systems, among others. The venom proteins offer a source for the development of drugs for the treatment of pain, cancer, infectious diseases, auto-immune diseases, allergies, and hypertension. Most pharmaceutical drugs have been derived from natural products (compounds discovered in nature). However, most organisms, including fishes, have never been examined for biologically active molecules (or compounds that affect the biochemistry of living things) that could be developed into potential drugs. In addition, pharmaceutical companies have recently de-emphasized natural products research and search for biologically active molecules by screening mass-produced combinations of compounds. Neither strategy has met expectations, and the number of new registered drugs continues to decrease dramatically. To date, most venom bioprospecting has focused on snakes, resulting in six stroke or cancer treatment drugs that are nearing U.S. Food and Drug Administration review. However, as fishes, not snakes, are now known to be the dominant venomous group among vertebrates, they represent a massive untapped resource of potentially medically beneficial compounds.

Poisonous Soapfish

In the new paper on the evolution of venomous fishes, Drs. Smith and Wheeler highlight an approach to drug discovery that involves resolving the family or phylogenetic tree of spiny-rayed fishes and the evolution of venom in this group. This first-ever phylogeny of venomous fishes, resolved in part via a month-long run on the Museum's parallel computing cluster and corroborated by checking the results against specimens in the Museum's extensive fish collection, provides a predictive "roadmap," or framework, that can guide the efficient discovery and exploitation of untapped fish venoms for potential pharmaceuticals.

This project was supported by funding from the National Aeronautics and Space Administration-Ames Fundamental Space Biology Program and National Science Foundation under Grant # DEB 045246.